Discharge system and discharge method for radioactive liquid effluent of nuclear power plant

Abstract

The invention belongs to the technical field of nuclear power plant radioactive liquid effluent emission, and provides a nuclear power plant radioactive liquid effluent emission system and an emission method thereof.The emission method comprises the steps that pretreated radioactive liquid effluent is atomized to form water mist; ambient air is obtained and sequentially subjected to filtering, dehumidification and heating treatment, and dry and hot air is formed; the water mist and the dry and hot air are mixed to form mixed gas, the temperature of the mixed gas is higher than the temperature of the external environment by 1 DEG C or above, and the humidity of the mixed gas is lower than the humidity of the external environment by 2% or above; and mixing the mixed gas with system exhaust air of the nuclear power plant to form airborne radioactive effluents, and discharging the airborne radioactive effluents to the external environment. According to the invention, the problem of discharging the radioactive liquid effluent of the small nuclear power plant without a receiving water body or not allowed to be discharged to the receiving water body can be solved.

Description

Technical Field

[0001] The present application relates to the technical field of discharge of radioactive liquid effluent from nuclear power plants, and in particular to a discharge system and a discharge method of radioactive liquid effluent from nuclear power plants. Background Art

[0002] Small nuclear power plants are small in scale, produce less waste, have greater safety advantages, are widely used, and are flexible in layout. They can be built in remote areas, cities, industrial parks, etc. Due to the diversity of plant site conditions, higher requirements are placed on the discharge plan of radioactive liquid effluents after treatment. In particular, for small nuclear power plants that have no receiving water bodies or are not allowed to discharge into receiving water bodies, in order to meet the discharge requirements in the "Regulations on Environmental Radiation Protection of Nuclear Power Plants" (GB 6249-2011), consider converting the treated radioactive liquid effluents that meet the emission limits into airborne radioactive effluents through appropriate process flows for discharge, thereby achieving liquid-to-gas discharge of radioactive liquid effluents. Through new discharge pathways, the discharge of radioactive liquid effluents from small nuclear power plants in areas without receiving water bodies or where discharge into receiving water bodies is not allowed is solved.

[0003] At present, there are sporadic practices of liquid-to-gas discharge technology for radioactive liquid effluents at home and abroad, but no clear technical route has been formed, and sometimes it is not the best discharge technical route. The existing liquid-to-gas discharge technology for radioactive liquid effluents mainly includes:

[0004] 1. Using air-carrying discharge stations to solve the problem of radioactive liquid effluent discharge: Based on the principle of air humidification, the air-carrying discharge technology increases the surface wind speed of the carrier medium (cloth strip) and the characteristic that the air humidity is usually lower than the saturated humidity. The treated radioactive liquid effluent sprayed on the cloth strip is discharged through the exhaust carrier of the ventilation system in the form of air-carrying to achieve airborne monitoring and discharge, thereby achieving the purpose of airborne discharge of radioactive liquid effluent. The water in the radioactive liquid effluent is discharged with the air in the form of steam.

[0005] However, the above solution has the following defects:

[0006] a) The process flow and facility layout of this scheme are relatively complex, and the requirements for facility land and internal layout are high. Since the method of spraying liquid radioactive effluent on the hanging cloth is adopted, the amount of dripping back is large, and the dripping waste liquid needs to be purified and recycled, and the treatment efficiency of the scheme is low;

[0007] b) The engineering application effect of this scheme is greatly affected by technical factors such as the type of hanging cloth, the material of the hanging cloth, and the spraying method. In addition, the final treatment of the hanging cloth as secondary waste needs to be considered, and the secondary waste output is high;

[0008] c) When the ambient temperature is lower than 6°C and the ambient humidity is higher than 80%, the operating effect is poor.

[0009] 2. Use natural evaporation ponds to evaporate liquid radioactive effluents: The natural evaporation pond discharge scheme is a treatment method that uses solar energy to evaporate and remove water from liquid radioactive effluents. It has simple requirements for operating facilities, does not require excessive daily maintenance, and is energy-saving, so the natural evaporation pond discharge scheme is more commonly used. However, natural evaporation ponds occupy a large area, require a long period of sunshine, and are greatly affected by rainfall, so the application of this method is subject to certain restrictions.

[0010] In addition, the above solution has the following defects:

[0011] a) This solution occupies a large area, requires longer sunshine hours, and the evaporation of the plant site needs to be greater than the rainfall, which limits its availability.

[0012] b) This plan poses the risk of invasion of surrounding organisms and introduction of radionuclides into the biosphere, and the mud produced after the evaporation of liquid radioactive effluents poses the risk of radioactive contamination to the surrounding soil and environment. The decommissioning of natural evaporation ponds will also bring about a large amount of site cleanup and environmental remediation work.

[0013] c) The emission method of this solution is to release the gas directly into the atmosphere without passing through a chimney, which poses a risk of not complying with the requirements of GB 6249-2011.

[0014] 3. Air-cooled tower: Liquid effluent is atomized by an atomization auxiliary device and then dispersed into the air in the tower. It completely evaporates into gaseous state by utilizing the relatively high temperature and high wind speed inside the tower compared to the external environment and the huge gas-liquid contact area after atomization, and is discharged into the atmosphere through the air outlet of the air-cooled tower. However, this scheme is suitable for nuclear power plant sites that use air-cooling technology, but it is necessary to carry out simulation research on the physical model of the air-cooled tower scheme when applying it in engineering.

[0015] 4. Water-cooled tower: Liquid effluent is atomized by the spray discharge device and dispersed into the air in the tower, and discharged into the atmosphere with the suction effect of the cooling tower. The water-cooled tower liquid-to-gas solution is suitable for nuclear power plant sites using water-cooled towers, where the atomized droplets of liquid effluent are not completely evaporated in the tower, but the unevaporated droplets will be discharged into the atmosphere with the humid air.

[0016] 5. Chimney: The evaporator is used to convert the liquid effluent into steam and discharge it through the nuclear island chimney. Due to the large changes in air humidity, this solution is suitable for sites in northern areas with relatively dry climates. After the exhaust gas leaves the tower, it will condense when it encounters cold, which will produce drifting and dripping, which requires further research.

[0017] 6. Single-construction emission facilities: two emission processes, atomization and evaporation, can be used to discharge liquid effluent from a separately constructed emission facility such as a chimney. Among them, the atomization emission process: the liquid effluent enters the atomization chamber through the emission pump, and is formed into uniform and fine small droplets through the spray device. At the same time, under the suction action of the induced draft fan, the air is inertially dusted and heated to the required temperature by the heater, and then passes through the air filter to remove sand and dust, and enters the high-pressure spray chamber. In the atomization chamber, the high-temperature air and the atomized droplets are fully mixed and humidified, and then sent to the emission chimney for elevated discharge. However, in engineering applications, it is necessary to analyze the heat and mass transfer phase change process of the air, and there is no clear technical route for practical application. Summary of the invention

[0018] In view of the above-mentioned shortcomings of the prior art, the present invention provides a nuclear power plant radioactive liquid effluent discharge system and a discharge method thereof to solve the problem of radioactive liquid effluent discharge in small nuclear power plants that have no receiving water bodies or are not allowed to discharge into receiving water bodies.

[0019] To achieve the above and related purposes, the present invention adopts the following technical solutions:

[0020] The first aspect of the present invention provides a method for discharging radioactive liquid effluent from a nuclear power plant, comprising the following steps:

[0021] atomizing the pretreated radioactive liquid effluent to form water mist;

[0022] Obtain ambient air and process it through filtering, dehumidification and heating in sequence to form dry hot air;

[0023] Mix water mist with dry hot air to form a mixed gas, the temperature of the mixed gas is higher than the temperature of the external environment by more than 1°C, and the humidity of the mixed gas is lower than the humidity of the external environment by more than 2%;

[0024] The mixed gas is mixed with the system exhaust air of the nuclear power plant to form airborne radioactive effluent and discharged into the external environment.

[0025] Furthermore, the particle size of the water mist is 1 μm to 10 μm.

[0026] Furthermore, the system exhaust meets at least one of the following conditions (a) to (b):

[0027] (a) The exhaust temperature of the system is 30℃~60℃;

[0028] (b) The humidity of the system exhaust air is 40% to 70%.

[0029] Furthermore, the method also includes: during the atomization process of the radioactive liquid effluent, detecting the activity concentration of the radioactive liquid effluent, and when the activity concentration does not meet the first preset discharge condition, subjecting the radioactive liquid effluent to secondary pretreatment.

[0030] Furthermore, the method also includes: during the mixing process of the water mist and the hot dry air, if condensed dripping liquid exists, the condensed dripping liquid is collected.

[0031] The second aspect of the present invention provides a radioactive liquid effluent discharge system for a nuclear power plant, comprising an atomization unit, an air handling unit, an air mixer, a gas collecting chamber and a chimney, wherein the atomization unit is a place where the pre-treated radioactive liquid effluent is atomized to form water mist; the air handling unit is a place where ambient air is obtained and filtered, dehumidified and heated in sequence to form dry hot air; the air mixer is a place where water mist and dry hot air are mixed to form a mixed gas, the temperature of the mixed gas formed by the air mixer is higher than the temperature of the external environment by more than 1°C, and the humidity is lower than the humidity of the external environment by more than 2%; the gas collecting chamber is a place where the mixed gas is mixed with the system exhaust air of the nuclear power plant to form airborne radioactive effluent; and the chimney is a place where the airborne radioactive effluent is discharged to the external environment.

[0032] Furthermore, the system also includes a waste liquid pretreatment unit, the atomization unit includes an ultrasonic humidifier, and the ultrasonic humidifier is connected to the waste liquid pretreatment unit pipeline.

[0033] Further, the air handling unit includes a fan, a ventilation filter, an air dehumidifier and an air heater.

[0034] Furthermore, the system also includes a water supply unit, which is connected to the air heater pipeline and is used to provide a heat source for the air heater.

[0035] Furthermore, the system also includes a nuclear island chilled water unit, which is connected to the air dehumidifier pipeline and is used to provide a cold source for the air dehumidifier.

[0036] Furthermore, the system also includes a radioactive hydrophobic collection unit, which is connected to the air mixer pipeline and is used to collect condensed dripping liquid in the air mixer.

[0037] Furthermore, the system also includes a nuclear island control area ventilation unit, which is connected to the air collecting chamber pipeline and is used to introduce system exhaust air into the air collecting chamber.

[0038] The beneficial technical effects of the present invention are:

[0039] The present invention atomizes the radioactive liquid effluent that meets the emission limit after pretreatment to form fine water mist; filters, dehumidifies and heats the acquired ambient air in sequence to form dry hot air, mixes the water mist with the dry hot air to form a mixed gas with a temperature greater than 1°C and a humidity less than 2% of the humidity of the external environment, so as to ensure that no condensation occurs; discharges the mixed gas to the gas collecting chamber at the lower part of the nuclear island chimney and mixes it with the system exhaust of the nuclear power plant for secondary mixing, and then discharges it from the chimney, so as to ensure that no "white fog" phenomenon occurs when the airborne radioactive effluent is discharged, and no condensation and dripping occurs after the airborne radioactive effluent is discharged into the external environment atmosphere. Thus, the monitoring and discharge of airborne radioactive effluent is realized, the purpose of liquid-to-gas discharge of radioactive liquid effluent is achieved, and the discharge requirements of GB 6249-2011 for radioactive liquid effluent of small nuclear power plants are met.

[0040] The system of the present invention fully combines the characteristics of small nuclear power plants and utilizes existing facilities, such as water supply units, nuclear island chilled water units, etc., to provide a liquid-to-gas discharge solution for small nuclear power plants, which has low radioactive liquid effluent dripback, high treatment efficiency, low secondary waste production, good site adaptability, and can achieve centralized discharge of airborne radioactive effluents, thereby solving the discharge problem of radioactive liquid effluents in small nuclear power plants that have no receiving water bodies or are not allowed to discharge into receiving water bodies.

[0041] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present application, and together with the specification, are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0043] Figure 1 This is a schematic diagram of an exemplary exhaust system of the present application.

[0044] Reference numerals

[0045] 1: Waste liquid treatment system; 2: Atomization unit; 3: Nuclear island sampling system; 4: Air mixer; 5: Radioactive drain collection system; 6: Air heater; 7: Water supply system; 8: Air dehumidifier; 9: Nuclear island chilled water system; 10: Ventilation filter; 11: Fan; 12: Air collection chamber; 13: Auxiliary plant control area ventilation system; 14: Chimney. DETAILED DESCRIPTION

[0046] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as the general understanding of a person of ordinary skill in the art to which the present invention belongs. It should be understood that certain features of the present invention (described in the context of separate embodiments for clarity) may also be provided in combination in a single embodiment. On the contrary, multiple features of the present invention (described in the context of a single embodiment for brevity) may also be provided separately or in any suitable combination or in any other described embodiment of the present invention when appropriate. Certain features described in the context of various embodiments will not be considered as essential features of those embodiments unless the embodiment is inoperable without those elements. The present invention is further described below by specific specific examples, but it should be noted that the specific process conditions and results described in the embodiments of the present invention are only used to illustrate the present invention, and the protection scope of the present invention cannot be limited thereto. All equivalent changes or modifications made according to the spirit and essence of the present invention should be included in the protection scope of the present invention.

[0047] First of all, it should be noted that the nuclear power plants referred to in this application are nuclear power plants, nuclear thermal power plants, and nuclear steam and heating plants, etc.

[0048] Radioactive effluent: Generally, radioactive materials discharged into the environment from nuclear power plants in the form of gas, aerosol, dust and liquid, which are diluted and dispersed in the environment.

[0049] LWT: Liquid Waste Treatment system, liquid waste treatment system.

[0050] NDS: Nuclear Island Drainage System, radioactive drainage collection system.

[0051] SAS: Sampling Analysis System, nuclear island sampling system.

[0052] HFS: Heat Feed Water System, water supply system.

[0053] NCW: Nuclear Island Chilled Water System, nuclear island chilled water system.

[0054] VAB: Auxiliary Building Controlled Area Ventilation System, auxiliary building controlled area ventilation system.

[0055] The present invention provides a method for discharging radioactive liquid effluent from a nuclear power plant, comprising the following steps:

[0056] atomizing the pretreated radioactive liquid effluent to form water mist;

[0057] Obtain ambient air and process it through filtering, dehumidification and heating in sequence to form dry hot air;

[0058] Mix water mist with dry hot air to form a mixed gas, the temperature of the mixed gas is higher than the temperature of the external environment by more than 1°C, and the humidity of the mixed gas is lower than the humidity of the external environment by more than 2%;

[0059] The mixed gas is mixed with the system exhaust air of the nuclear power plant to form airborne radioactive effluent and discharged into the external environment.

[0060] In some embodiments, the present application converts radioactive liquid effluent into water mist and mixes it with dry hot air. This is mainly based on the fact that dry hot air can greatly improve the absorption efficiency of radioactive liquid effluent water mist, thereby improving the environmental adaptability of the method of the present application. Compared with the existing airborne belt emission technology and natural evaporation pond technology, which are greatly affected by the environmental conditions of the plant site, the method of the present application can be applied to a variety of plant sites and can be used for plant sites with more stringent environmental conditions.

[0061] In some embodiments, the water mist of the present application is fully mixed with the dry hot air. In order to avoid dripping after mixing, it is necessary to control and adjust the parameters of the dry hot air and the water mist, mainly including flow rate, temperature and humidity. The standard is that no condensation occurs after the water mist is added to the dry hot air. Specifically, the temperature of the mixed gas after the water mist and the dry hot air are mixed is more than 1°C higher than the ambient temperature, and the humidity after the water mist and the dry hot air are mixed is more than 2% lower than the ambient humidity.

[0062] In some embodiments, the mixed gas of the present application is mixed with the system exhaust air for a second time to ensure that no "white fog" phenomenon occurs when the airborne radioactive effluent is discharged, and that no condensation and dripping occurs after the airborne radioactive effluent is discharged into the external environment atmosphere.

[0063] In some embodiments, the particle size of the water mist is 1 μm to 10 μm. The radioactive liquid effluent of the present application is atomized to form fine water mist, which is conducive to the absorption of the dry hot air.

[0064] In some embodiments, the system exhaust meets at least one of the following conditions (a) to (b): (a) the temperature of the system exhaust is 30°C to 60°C; (b) the humidity of the system exhaust is 40% to 70%. The exhaust temperature and humidity of this application refer to the engineering experience values. When the operating project is controlled according to this condition, there is no "white fog" phenomenon at the chimney outlet. This application is set according to this condition, and the goal is to ensure that no condensation dripping occurs after the secondary mixing is discharged into the atmosphere.

[0065] In some embodiments, the method of the present application further comprises: during the atomization process of the radioactive liquid effluent, detecting the activity concentration of the radioactive liquid effluent, and when the activity concentration does not meet the first preset discharge condition, performing secondary pretreatment on the radioactive liquid effluent. The first preset discharge condition of the present application is a prescribed allowable discharge limit.

[0066] In some embodiments, the method of the present application further includes: during the mixing process of water mist and dry hot air, if condensed dripping liquid exists, the condensed dripping liquid is collected to reduce the impact on the humidity of the mixed gas.

[0067] The present invention also combines the characteristics of small nuclear power plants such as small scale, small waste production, and diversity of plant sites, and fully utilizes the sampling, cold source, heat source, ventilation, waste liquid treatment, waste liquid collection, centralized discharge and other functions that are usually set up in small nuclear power plants. A nuclear power plant radioactive liquid effluent discharge system is developed for small nuclear power plants, which has low dripping back in the liquid-to-gas process, high treatment efficiency, low secondary waste production, good plant site adaptability, and meets the emission requirements of regulatory standards.

[0068] like Figure 1 As shown, the radioactive liquid effluent discharge system of a nuclear power plant of the present invention comprises an atomizing unit 2, an air handling unit, an air mixer 4, a gas collecting chamber 12 and a chimney 14, wherein the atomizing unit 2 is a place where the pre-treated radioactive liquid effluent is atomized to form water mist; the air handling unit is a place where ambient air is obtained and filtered, dehumidified and heated in sequence to form dry hot air; the air mixer 4 is a place where water mist and dry hot air are mixed to form a mixed gas, the temperature of the mixed gas formed by the air mixer 4 is higher than the temperature of the external environment by more than 1°C, and the humidity is lower than the humidity of the external environment by more than 2%; the gas collecting chamber 12 is a place where the mixed gas is mixed with the system exhaust of the nuclear power plant to form airborne radioactive effluent; and the chimney 14 is a place where the airborne radioactive effluent is discharged to the external environment.

[0069] In some embodiments, the system of the present application further includes a waste liquid pretreatment unit, and the atomization unit 2 includes an ultrasonic humidifier, which is connected to the waste liquid pretreatment unit by a pipeline. Furthermore, the waste liquid pretreatment unit of the present application is an LWT waste liquid treatment system 1. In the present application, the radioactive liquid effluent that meets the emission requirements after being treated by the LWT system is sent to the ultrasonic humidifier, and the radioactive liquid effluent is atomized into a fine water mist of 1μm to 10μm by ultrasound, and the water mist is sent to the air mixer 4. The parts of the ultrasonic humidifier that are in direct contact with the radioactive liquid effluent are made of stainless steel, and the mist production capacity is not less than 100L / h. The upper part of the ultrasonic humidifier is provided with a radioactive liquid effluent inlet and a water mist outlet, and the bottom is provided with a drain. A sampling pipeline is arranged on the drain pipe, and the sampling pipeline is connected to the SAS nuclear island sampling system 3.

[0070] Furthermore, after the liquid radioactive effluent at the bottom of the ultrasonic humidifier is sampled and analyzed by the nuclear island sampling system 3 (SAS), if the sampled radioactive activity concentration exceeds the prescribed emission limit, it will be returned to the front end of the waste liquid treatment system 1 (LWT) for further purification.

[0071] Furthermore, the ultrasonic humidifier of the present application is provided with a liquid level alarm. The present application provides a special retention tank for the ultrasonic humidifier to collect all waste liquid when the ultrasonic humidifier is damaged, so as to avoid leakage of radioactive liquid into the environment.

[0072] Furthermore, the present application adopts an ultrasonic humidifier because its principle is to atomize the radioactive liquid effluent into water mist of 1μm to 10μm through ultrasound. The atomization process is smooth and uniform, and the mixing process is controlled based on the standard that no condensation occurs after the water mist is added to the dry hot air. Basically, no dripping will be generated. Therefore, the dripping amount of the present application will be much lower than the dripping amount after spraying the hanging cloth in the air carrier emission technology, which improves the processing efficiency and reduces the purification process of the dripping liquid.

[0073] In addition, this application will not introduce new secondary waste except for the equipment itself, while the air-borne emission technology will introduce a large amount of hanging cloth as secondary waste, and the mud produced after evaporation in the natural evaporation pond will also be used as secondary waste. It is also necessary to consider a large amount of site cleaning and environmental remediation work during the decommissioning stage.

[0074] In some embodiments, the air handling unit of the present application includes a fan 11, a ventilation filter 10, an air dehumidifier 8 and an air heater 6. The fan 11 of the present application is used to extract fresh air from the environment, and a centrifugal fan 11 made of carbon steel is selected.

[0075] Furthermore, the ventilation filter 10 of the present application is used to remove impurities in the fresh air of the environment and purify the fresh air, and a coarse-effect filter made of glass fiber is selected.

[0076] In some embodiments, the system further comprises a nuclear island chilled water unit, which is connected to the air dehumidifier 8 by a pipeline to provide a cold source for the air dehumidifier 8. The nuclear island chilled water unit of the present application is a NCW nuclear island chilled water system 9.

[0077] Furthermore, the air dehumidifier 8 of the present application is a stainless steel shell and tube heat exchanger, which uses the nuclear island chilled water system 9 (NCW) already equipped in the small nuclear power plant as a cold source to condense and dehumidify the moisture in the ambient air purified by the ventilation filter 10 to reduce the moisture content of the ambient air. After condensation and dehumidification, the absolute moisture content of the ambient air drops to below 6g / kg.

[0078] In some embodiments, the system further comprises a water supply unit, which is connected to the air heater 6 by a pipeline and is used to provide a heat source for the air heater 6. The water supply unit of the present application is a HFS water supply system 7.

[0079] Furthermore, the dehumidified ambient air of the present application enters the air heater 6 for heating and becomes dry hot air, the heat source comes from the water supply system 7 (HFS) equipped in the small nuclear power plant, and the temperature of the heated dry hot air is greater than 30° C. The air heater 6 is also a stainless steel shell and tube heat exchanger.

[0080] Furthermore, the present application makes full use of the existing cold source and heat source system of a small nuclear power plant to dehumidify and heat the ambient air, thereby obtaining dry hot air mixed with the water mist at the outlet of the ultrasonic humidifier.

[0081] In some embodiments, the system further comprises a radioactive hydrophobic collection unit, which is connected to the air mixer 4 by a pipeline and is used to collect condensed dripping liquid in the air mixer 4. The radioactive hydrophobic collection unit of the present application is an NDS radioactive hydrophobic collection system 5.

[0082] Furthermore, the air mixer 4 of the present application is provided with temperature and humidity measuring instruments so as to control the temperature and humidity of the exhaust gas from the air mixer 4 to the plenum 12 at the lower part of the chimney 14 to meet the set requirements. If a small amount of condensed dripping liquid still appears in the air mixer 4, it will be sent to the waste liquid collection pit by the radioactive hydrophobic collection system 5 (NDS).

[0083] In some embodiments, the system further includes a nuclear island control area ventilation unit, which is connected to the plenum chamber 12 by a pipeline and is used to introduce system exhaust air into the plenum chamber 12. The nuclear island control area ventilation unit of the present application is a VAB auxiliary plant control area ventilation system 13. The mixed gas discharged from the air mixer 4 of the present application enters the plenum chamber 12 at the lower part of the chimney 14, and is fully mixed with the exhaust air of the nuclear island auxiliary plant control area ventilation system 13 and then discharged to the atmosphere through the chimney 14. The exhaust air temperature of the auxiliary plant control area ventilation system 13 is controlled between 30°C and 60°C, and the exhaust air humidity is controlled between 40% and 70%. The exhaust air temperature and humidity refer to the engineering experience values. When the operating project is controlled according to this condition, there is no "white fog" phenomenon at the outlet of the chimney 14. The present application is set according to this condition, and the goal is to ensure that no condensation dripping occurs after the secondary mixing is discharged into the atmosphere.

[0084] In some embodiments, the present application utilizes the chimney 14 provided in the nuclear power plant to realize centralized discharge of radioactive liquid effluent after liquid-to-gas conversion, thereby meeting the requirement in regulatory standards that airborne radioactive effluent must be purified before being released into the atmosphere through the chimney 14, while existing air-borne emission technology and natural evaporation pond technology cannot meet this requirement.

[0085] In some embodiments, the present application Figure 1 The detailed setting information of the valves in the system is not shown. It is necessary to ensure that the valves on the pipelines are straight-through valves to reduce the possibility of pipeline resistance and blockage. The valve sealing materials have sufficient radiation resistance to ensure the expected service life. The frequently operated valves are electric valves that can be remotely operated from the control panel. All remote control valves provide valve position indication. The valves that are not frequently operated are manual valves.

[0086] In some embodiments, relevant interfaces are also provided on each unit and device of the system of the present application to complete the connection between each device.

[0087] In some embodiments, the present application uses an ultrasonic humidifier, an air dehumidifier 8, an air heater 6 and an air mixer 4 in combination, and the radioactive liquid effluent that has been treated and meets the emission limit is atomized by the ultrasonic humidifier, and then mixed with the dry hot air dehumidified and heated by the air dehumidifier 8 and the air heater 6 in the air mixer 4. After monitoring the temperature and humidity of the mixed gas to be basically consistent with the environmental conditions, it is discharged to the lower air collecting chamber 12 of the nuclear island chimney 14, and discharged through the chimney 14 with the exhaust air of the nuclear island auxiliary plant control area ventilation system 13 (VAB) to achieve airborne monitoring and emission, thereby achieving the purpose of liquid-to-gas emission of radioactive liquid effluent, solving the emission problem of liquid radioactive effluent from small nuclear power plants without receiving water bodies or not allowed to discharge into receiving water bodies, and controlling the radioactive release to meet the limit values ​​specified in GB 6249-2011, thereby minimizing the radioactive pollution to the environment and the public.

[0088] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for discharging radioactive liquid effluent from a nuclear power plant, It is characterized in that The following steps are involved: atomizing the pretreated radioactive liquid effluent to form water mist; Obtain ambient air and process it through filtering, dehumidification and heating in sequence to form dry hot air; Mixing the water mist with the hot dry air to form a mixed gas, wherein the temperature of the mixed gas is higher than the temperature of the external environment by more than 1°C, and the humidity of the mixed gas is lower than the humidity of the external environment by more than 2%; The mixed gas is mixed with the system exhaust air of the nuclear power plant to form airborne radioactive effluent and discharged into the external environment.

2. The discharge method according to claim 1, It is characterized in that The particle size of the water mist is 1 μm to 10 μm.

3. The discharge method according to claim 1, It is characterized in that The system exhaust meets at least one of the following conditions (a) to (b): (a) The exhaust temperature of the system is 30°C to 60°C; (b) The humidity of the exhaust air of the system is 40% to 70%.

4. The discharge method according to claim 1, It is characterized in that The method further includes: during the atomization process of the radioactive liquid effluent, detecting the activity concentration of the radioactive liquid effluent, and when the activity concentration does not meet the first preset discharge condition, performing secondary pretreatment on the radioactive liquid effluent.

5. The discharge method according to claim 1, It is characterized in that The method further comprises: if condensed dripping liquid exists during the mixing process of the water mist and the hot dry air, collecting the condensed dripping liquid.

6. A radioactive liquid effluent discharge system for a nuclear power plant, It is characterized in that It includes an atomization unit, an air handling unit, an air mixer, an air collection chamber and a chimney. The atomization unit is a place where the pre-treated radioactive liquid effluent is atomized to form water mist; the air handling unit is a place where ambient air is obtained and filtered, dehumidified and heated in sequence to form dry hot air; the air mixer is a place where the water mist is mixed with the dry hot air to form a mixed gas, the temperature of the mixed gas formed by the air mixer is higher than the temperature of the external environment by more than 1°C, and the humidity is lower than the humidity of the external environment by more than 2%; the air collection chamber is a place where the mixed gas is mixed with the system exhaust of the nuclear power plant to form airborne radioactive effluent; the chimney is a place where the airborne radioactive effluent is discharged to the external environment.

7. The exhaust system according to claim 6, It is characterized in that The system further comprises a waste liquid pretreatment unit, the atomization unit comprises an ultrasonic humidifier, and the ultrasonic humidifier is connected to the waste liquid pretreatment unit through a pipeline.

8. The exhaust system according to claim 6, It is characterized in that The air handling unit includes a fan, a ventilation filter, an air dehumidifier and an air heater.

9. The exhaust system according to claim 8, It is characterized in that The system further comprises a water supply unit, which is connected to the air heater pipeline and is used to provide a heat source for the air heater.

10. The exhaust system according to claim 8, It is characterized in that The system further comprises a nuclear island chilled water unit, which is connected to the air dehumidifier pipeline and is used to provide a cold source for the air dehumidifier.

11. The exhaust system according to claim 6, It is characterized in that The system further comprises a radioactive hydrophobic collection unit, which is connected to the air mixer pipeline and is used for collecting condensed dripping liquid in the air mixer.

12. The exhaust system according to claim 6, It is characterized in that The system further comprises a nuclear island control area ventilation unit, which is connected to the air collecting chamber pipeline and is used for introducing system exhaust air into the air collecting chamber.

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